Conventional technology thermistors are constructed by either: placing a bolus of a prepared paste of thermistor material (commercially available) between two wires, then firing the bolus at high temperature to result in an irregular “ball” of thermistor material with wires extending outward for electrical connection. This arrangement, if very fine wires are used, can isolate the thermistor element from surrounding heat sinks by virtue of the relatively small metal area involved in the wires. Or, thick-film printing of thermistor paste onto a substrate, wherein electrical connections are made by preparing the substrate with two or more metallic traces before deposition, or by metalizing the substrate prior to deposition of the thermistor, then metalizing the upper surface of the thermistor in a second step.
In either case extant thermistor production uses common electronic substrates such as Alumina. These substrates have high conduction of heat, rendering the resulting thermistors unsuitable for low-power bolometry. Further, such thermistors are made as larger sheets and sawed, resulting in thermistors that are too large to use for bolometry.
Accordingly, there is a long felt need in the art for a thick-film process that constructs very small thermistors on a substrate selected for low heat transfer. Further, thermal isolation needs to be enhanced by making the planar electrodes from a metal with lower heat transfer than typical electrical metals.